| Flexible direct current system(HVDC)is a new transmission technology based on voltage source converter,self turning off device and pulse width modulation technology.This transmission technology has the advantages of supplying power to passive network,no commutation failure,no communication between converter stations and easy to form multi terminal DC system.In recent years,with the continuous expansion of urbanization,the high-density access of distributed power generation and renewable energy and the wide use of a large number of DC loads,how to reasonably develop and effectively consume renewable energy,how to meet the power demand of large cities How to further improve the power supply quality and enhance the controllability of the power grid system is a great challenge for the power grid.Compared with the traditional AC distribution network,the DC distribution network constructed by flexible DC technology can save a lot of DC / AC converter links and improve the operation efficiency of the system;It can increase the power supply capacity and radius of the system and reduce the occupied area of urban land;It can reduce the electromagnetic radiation on the line and reduce the interference to the communication system.In addition,it can also solve a series of power quality problems such as large line loss of the existing AC distribution network,voltage fluctuation,grid harmonic and three-phase imbalance,and greatly improve the reliability and controllability of urban distribution.Therefore,it is a distribution mode with great technical advantages and development potential.In the future,the power electronization of power system has become a development trend and an important research direction.Power electronic devices play an important role in the access of distributed power to power grid,flexible control technology of power flow,customized demand of current source and load DC.DC distribution network technology is an effective carrier based on power electronic devices connected to the power grid.It has many advantages,such as stable control,high quality of power supply,improved reliability of power supply,flexible control of distributed power supply and so on.In the future,power electronization of power system has become a development trend and important research direction.Power electronic devices play an extremely important role in the connection of distributed generation to power grid,flexible control technology of power flow,customized current source demand and load DC.DC distribution network technology is an effective carrier based on power electronic devices connected to the power grid.It has many advantages,such as stable control,high power supply quality,improving power supply reliability,flexible control of distributed generation and many other things.However,due to the fast response,small inertia and poor anti disturbance of power electronics,it is even easy to cause the resonance problem of AC / DC system.Under this background,this paper takes the flexible DC distribution network as the research object,analyzes and studies the operation mode,start stop control and energy optimization management method of the flexible DC distribution network.The full text is based on the analysis of the main circuit,electrical parameters and operation mode of the medium voltage DC distribution system,this paper studies the connection mode,capacity and voltage level selection,topology of the flexible DC distribution network,and proposes a medium voltage DC system structure based on multi terminal interconnection.AC frequency and DC voltage are the indexes reflecting the energy balance between the system power supply and load.This paper studies the start and stop control technology of the key technical equipment of the flexible DC distribution network,and puts forward the start and stop control strategy of the key technical equipment of the system according to the related indexes such as frequency and voltage.Considering the stability,safety,economy and other performance in operation,the operation optimization of DC distribution network is actually a multi-objective optimization problem.Focusing on that AC frequency and DC voltage are the indicators reflecting the energy balance between system power supply and load,this paper studies the start and stop control technology of key technical equipment of flexible DC distribution network,and puts forward the start and stop control strategy of key technical equipment of the system according to relevant indicators such as frequency and voltage.An energy optimization and management method of flexible DC distribution network based on particle swarm optimization(PSO)is proposed,and the final power flow optimization instructions are obtained by solving the model.In the simulation software PSCAD,the simulation model of DC distribution network is built,and the start-up and stop control of the key technical equipment of the flexible DC distribution network,the energy optimization and management method of the flexible DC distribution network based on particle swarm optimization algorithm,and the operation mode are analyzed,and the simulation verification of each control strategy is carried out.The simulation results verify the validity and correctness of the proposed method.Based on the summary and consideration of the actual project of the flexible DC distribution network,this paper analyzes and studies the start and stop control and energy optimization management method of the flexible DC distribution network,which is of great significance for the key parameters and calculation basis,and for the guidance of the actual project. |
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